Install a very comprehensive icon set and apply it. Something like adwaita-icon-theme usually has all icons. Then open the same window and see what the icons are. Then look for the icon in the iconset to get the name. Copy them into your current install.

How do i become super user?
Wear your underpants on the outside and put on a cape.

Jack, if you are under LXDE desktop, you should have lxappearance package installed.

Then, you should have some icon themes under /usr/share/icons (available to all users) or under /home/guest/.icons (only available to guest user in this case). There's also /home/guest/.local/share/icons which seems to be a new "trending" location for all this stuff. In short, those are the places where you put your custom icons, themes, fonts. etc.